1. Field of the Invention
This invention relates to a magnetic disk cartridge comprising a small-diameter thin magnetic disk which is rotated for recording and reproducing information. This invention particulary relates to a magnetic disk cartridge provided with an improved means for cleaning the magnetic disk.
2. Description of the Prior Art
Floppy disks are widely used as recording media for computers because they are easy to handle and low in cost. The floppy disk comprises a disk-shaped base made of flexible polyester sheet or the like, and a magnetic material layer overlaid on opposite surfaces of the disk-shaped base. The floppy disk is rotated for magnetically recording information on the magnetic material layer by use of a magnetic head.
Utilizing the aforesaid advantages of the floppy disk and the advantage that a magnetic recording medium has over a silver halide photographic film in that the magnetic recording medium can be reused, there have been proposed micro-floppy disks which are smaller than the compact floppy disk and is easier to handle.
There have heretofore been various attempts made to improve the reliability of the floppy disk. For example, the floppy disk has been provided with a hard case, and a dust preventing shutter provided at the aperture of the hard case. Also, it has been proposed to use a smaller magnetic disk as the image recording medium in electronic still cameras. The magnetic disk used for such still cameras comprises a small-diameter thin magnetic recording medium, and a hub secured to the center of the magnetic recording medium. The magnetic disk is rotatably housed in a small case provided at the center thereof with a hub hole for exposing the hub of the magnetic disk. The case also has magnetic head insertion apertures in the upper and lower surfaces for exposing a part of the magnetic disk. The combination of the magnetic disk with the case is called a magnetic disk cartridge.
In the magnetic disk cartridge of the aforesaid type, a liner fabricated of a nonwoven rayon fabric, a nonwoven polyester fabric or the like is positioned between the magnetic disk and an inner wall surface of the case so that the liner lightly contacts the recording surface of the magnetic disk and removes dust or the like from the recording surface as the magnetic disk rotates. Also, a lifter made of a synthetic resin or the like is positioned between the inner wall surface of the case and the liner. One end portion of the lifter is secured to the inner wall surface of the case, and the other end portion thereof is bent up away from the inner wall surface to form a rising portion which resiliently pushes up the liner. The lifter urges the liner into contact with the magnetic disk with a uniform force so that sufficient cleaning effects are obtained. However, in the conventional magnetic disk cartridge, since the rising portion of the lifter is formed by mechanically bending a flat lifter member, the rising portion is weakened by long use of the magnetic disk cartridge, and the force with which the liner is pushed by the rising portion becomes too small to allow the liner to contact the magnetic disk with sufficient force, and the cleaning effect deteriorates gradually. Also, as the lifter weakens, the running torque of the magnetic disk decreases, and it is therefore not always possible to maintain a constant running torque.